Matching Prop to Outboard

[Jekyll]

I recently purchased a 5 metre Stessco aluminium bowrider from a local dealer, fitted with a 2003 Yamaha 70hp two stroke. The engine runs sweet as a nut, and the boat itself is a thing of beauty and a joy forever ... BUT

I'm only getting around 4500 RPM at WOT, which would seem to be way low for this engine. I'm looking at putting a different prop on the outboard, to increase my RPM at WOT and improve holeshot and decrease slow trolling speed. So riddle me this:

1. The engine currently has a SOLAS 3 bladed 13.25 x 17 prop. Max speed at 4500RPM is a tick over 30mph by GPS at slack water. The Yamaha manual recommends a 13 x 17 prop
2. I'm considering a 13 x 15 or 13 x 14 aluminium prop as a replacement. Good idea or not?
3. What is a "propeller mark"? The Yamaha manual for this engine specifies a propeller mark of 'K', whilst the full description on the SOLAS prop currently fitted is "D 3x13.25x17R". I assume the D is the propeller mark? Any significance to this?
4. I'm usually carrying myself, my wife, and my two kids (10 and 8) in the boat when fishing (just to give you an idea of the usual load)
5. I've had the linkages checked, just in case full throttle on the throttle arm was not giving full throttle movement on the outboard. Everything checks out OK there.
6. Anyone know of a place I can source reasonably priced aluminium propellers around the Brisbane area?

Your advice appreciated :)

[luckyone]

ring solas or get onto ther web sitethere up the north coast and they are very helpfull. they will solve your problem. have used them before and was very sastifide

[Jekyll]

Yup rang Solas and they suggested the 15" pitch would be about right. Will have to run on the 17 temporarily until finances allow ... wife is starting to complain about all the 'jewellery' for the boat :)

[Scalem]

So you are a family man who reports to a finance manager too?? ;D

I have the same problem!! I used to run two props on my Yammy of the same HP. The 17" was for general use and the 15" was for water skiing as I am involved as a ski boat driver every September school holidays. The boat is a 15" Mustang fibreglass. Eventually I got tired of changing props, so the guys down at southport "cupped" the 15" a little on the outer edge of the blades, which gave me very similar top end speed, but more bite out of the hole when pulling single skiers out. Will also give you more revs, but to my way of thinking I don't go past 5000rpm anyhow, which it won't take much to get those revs out of a 15" prop.

Scalem